"Garry's Mod (unofficially abbreviated as GMod) is a nonlinear physics game that allows the player to manipulate objects and experiment with physics. Garry's Mod has been available on Steam's content delivery service since November 29, 2006. Even though Garry's Mod is a standalone game, it requires the user to own at least one Source game on Steam such as Half-Life 2, Team Fortress 2, Counter-Strike: Source, Left 4 Dead, and Left 4 Dead 2. Garry's Mod allows players to manipulate props created by the community or included in any Source engine game installed on their computers using the Physics Gun, a tool that allows objects to be picked up from any distance, adjusted and frozen in place. A second, multi-purpose gun called the Tool Gun can perform various tasks, including but not limited to welding props together, attaching them to each other using ropes and creating controllable winches and wheels. The Tool Gun is also used to control many add-ons created by the community. Another popular Garry's Mod concept is ragdoll posing. The player has the ability to create a ragdoll model from a Source game and pose it using a variety of tools. Garry's Mod takes advantage of the Source engine's modified version of the Havok Physics Engine, which allows the players build contraptions that follow the laws of physics." Source: Wikipedia, Garry's mod , available under the CC-BY-SA License.